The present disclosure relates to a rising arrangement for tribological contact areas for cooling and lubricating the latter and in particular to a rotary vane pump with an adjustable lifting ring, which is provided with a rinsing arrangement according to the disclosure.
In principle, tribology examines friction, lubrication and wear of bearings, guides, gears, motors and other machine elements. In addition to developing suitable lubricants, questions in respect of material selection, surface coating and surface topography are at the forefront of current developments. In addition to questions from mechanical engineering, there are numerous further fields in which friction and wear are of great importance, for example in endoprosthetics.
In the case of hydraulic machines such as e.g. rotary vane pumps, but also in the case of other machines with components that are in frictional contact, there is the basic problem of adhesive wear and abrasive wear resulting therefrom at so-called tribological contact points, particularly if a normal force acts on these contact points/areas and the latter merely move microscopically, i.e. only very little, with respect to one another, at least over a certain period of time. There is virtual dry operation at the contact point, in which the tribological partner “fluid” is barely or not at all present. As a result, there is overheating of the areas, coking of the possibly present remaining fluid, frictional corrosion and, not least, premature adhesive wear. Adhesive wear may also occur in the case of macro-movements where very much frictional heat is generated.
A pump unit with a main pump and a charge pump, which has an adjustable delivery volume and is embodied as a rotary vane pump, is mentioned here as a user-related example, as known, inter alia, from the prior art, for example as per DE 10 2007 032 103 A1.
This pump unit comprises an axial piston pump as the main pump, the rotary vane pump also being driven via the driveshaft thereof. Here, the rotor of the rotary vane pump is seated directly on the extended driveshaft of the main pump in a rotationally fixed fashion. Here both pumps are housed in a common housing. As an alternative, the rotary vane pump can also have its own driveshaft, which is coupled to the driveshaft of the main pump via a bushing, for example.
A number of slits lying substantially in axial planes running parallel to the axis of the rotor have been introduced into the rotor of the rotary vane pump. Each slit holds a radially moveable pump vane, which rests against the internal wall of a lifting ring in a sealing fashion as a result of the centrifugal force, which occurs when the rotor rotates, and an occasionally additionally present restricted guidance and slides along said lifting ring. In respect of its relative position with respect to the rotational axis of the rotor, the lifting ring is, with the pump vanes, mounted in the housing in a displaceable fashion with respect to the radial direction in order thus to change the measure of eccentricity of the inner wall of the lifting ring with respect to the rotational axis, and hence to change the swept volume of the rotary vane pump. According to DE 10 2007 032 103 A1, the lifting ring is mounted externally in displaceable fashion in diametrically opposing parallel bearing areas on corresponding counter areas of the housing. The adjustment is brought about as a function of the output pressure of the rotary vane pump, wherein the pressure acts on an operative area on the lifting ring, determined by the spacing of the two bearing areas and the axial extent of the lifting ring, and acts against a spring.
The ratio between guidance length and guidance width of the lifting ring in the pump housing is not very expedient in the known rotary vane pump. As this ratio decreases, the risk of jamming increases. This is linked to the lever length available to the frictional forces.
In view of these circumstances, it is the object of the present disclosure in general to design so-called tribological contact areas such that the fictional forces are kept low. In particular, an increase in the frictional forces as a result of adhesive and abrasive wear to have and as a result of excessive heat influx should be kept low during operation. A particular goal of the disclosure is to improve the tribological contact areas between a lifting ring and its sliding partner in the case of a rotary vane pump such that the frictional forces, and hence the risk of the lifting ring jamming, are kept low.